Surveillance of Important Oyster Diseases in Taiwan

for 2025–2026

Chieh-Hao Wu

Abstract

Oysters are an economically important bivalve species in Taiwan. To mitigate the impact of imported oysters and enhance the competitiveness of the domestic industry, the Institute initiated a major disease surveillance program in 2025 to clarify the causes of the recent decline in domestic production. The surveillance covers main farming areas including Yunlin, Chiayi, and Tainan, focusing on the detection and case analysis of major pathogens listed by WOAH and NACA, as well as investigating the correlation between disease and environmental factors such as climate and geography. Furthermore, following the initial detection of Marteilioides chungmuensis infection in cultured Portuguese oysters (Crassostrea angulata) along the southern coast in February 2023, the Institute has maintained continuous pathogen monitoring. This program aims to enable early warning and detection of invasive exotic pathogens, monitor domestic disease status, and effectively safeguard Taiwan's oyster aquaculture industry.

Whole-Genome Sequence Analysis of Decapod Iridescent Virus 1

Yi-Ping Lu

Abstract

Decapod iridescent virus 1 (DIV1) is a high-consequence crustacean pathogen that induces nearly 100% cumulative mortality in white shrimp (Litopenaeus vannamei) while causing asymptomatic, latent infections in redclaw crayfish (Cherax quadricarinatus). To elucidate the molecular basis underlying this distinct phenotypic dichotomy, we established a hybrid de novo sequencing pipeline that reconciled critical assembly artifacts in public reference genomes and refuted previously suspected polymorphic loci. The fully curated 167,660-bp genome encodes 166 verified coding sequences (GenBank: PZ829668, PZ829669). Cross-host comparative alignments revealed near-perfect sequence identity (99.99%–100%) across isolates, confirming that differential virulence is primarily governed by host susceptibility rather than viral genetic divergence. Furthermore, phylogenomic reconstruction across 15 iridovirus lineages delineated an autonomous, four-tier safeguarding machinery underpinning DIV1 replication fidelity: (1) core topoisomerases and DNA polymerase; (2) double-strand break repair driven by RAD50 and Holliday junction resolvase (a pathway lost in vertebrate iridoviruses); (3) genomic integrity maintenance via a tandem expansion of 14 NAD-dependent DNA ligase copies; and (4) nucleotide pool balance regulated by dTMP kinase and dUTPase. Unlike vertebrate iridoviruses that have undergone reductive evolution, DIV1 retains an autonomous repair toolkit to preserve genomic stability across primitive invertebrate hosts, thereby offering actionable molecular targets for precision diagnostics and aquaculture biosecurity.

Report on Attending the 28th SEACFMD

Sub-Commission Meeting in Mongolia

Cheng-Ju Pan

Abstract

The World Organisation for Animal Health (WOAH), through the South-East Asia, China and Mongolia Foot and Mouth Disease (SEACFMD) Campaign, continues to promote regional cooperation on foot and mouth disease (FMD) prevention and control by providing technical support, regional coordination, and capacity building for its members. The SEACFMD Campaign also serves as an important platform for regional collaboration in the prevention and control of transboundary animal diseases. The 28th SEACFMD Sub-Commission Meeting coincided with the first year of implementation of the SEACFMD Roadmap 2026–2030. In addition to reviewing the global and regional FMD situation and associated risks, the meeting focused on the risk posed by the incursion of FMD virus serotype SAT1, developments in the global FMD control strategy, the implementation plan for the SEACFMD Roadmap 2026–2030, its monitoring and evaluation framework, and mechanisms for regional cooperation. Participation in this meeting provided an opportunity to obtain current information on global and regional FMD epidemiological trends and control strategies, as well as to learn from the experiences of participating countries in disease surveillance, laboratory diagnosis, and disease control practices. The exchange of information and experiences also strengthened regional cooperation and international collaboration, offering valuable references for the continued improvement of FMD surveillance, diagnosis, and control strategies in Taiwan.